Some properties of saliva such as buffer capacity, secretion rate, anti-bacterial activities and effects on bacterial colonization are suggested to be of importance for the development of dental caries. Such properties would be dependant upon the biosynthesis and secretion of substances from the salivary glands. The aim of this study is to investigate the effect of manutrition on the composition of whole saliva and on incidence of caries in rats fed sucrose. Twenty rats were fed nutritionally adequate diets by gastric intubation. Ten of these received a supplement of sucrose and 10 of starch. Another 20 rats were fed the basic diet diluted with an equal volume of water; ten were supplemented with sucrose and with starch. The supplements are distributed 17 times daily. Striking difference in caries score in the two sucrose fed groups (6.5 - 35.0). No differences were evident in the activity of lactoperoxidase or lysozyme.